// reference: https://github.com/wechat-miniprogram/threejs-miniprogram/blob/master/example/loaders/gltf-loader.js
// before: var URL = window.URL || window.webkitURL;
// after: var URL = {};
// date: 2019-10-31

module.exports = function registerGLTFLoader(THREE) {

  /**
   * @author Rich Tibbett / https://github.com/richtr
   * @author mrdoob / http://mrdoob.com/
   * @author Tony Parisi / http://www.tonyparisi.com/
   * @author Takahiro / https://github.com/takahirox
   * @author Don McCurdy / https://www.donmccurdy.com
   */
  
    THREE.GLTFLoader = (function () {
  
      function GLTFLoader(manager) {
  
        this.manager = (manager !== undefined) ? manager : THREE.DefaultLoadingManager;
        this.dracoLoader = null;
        this.ddsLoader = null;
  
      }
  
      GLTFLoader.prototype = {
  
        constructor: GLTFLoader,
  
        crossOrigin: 'anonymous',
  
        load: function (url, onLoad, onProgress, onError) {
  
          var scope = this;
  
          var resourcePath;
  
          if (this.resourcePath !== undefined) {
  
            resourcePath = this.resourcePath;
  
          } else if (this.path !== undefined) {
  
            resourcePath = this.path;
  
          } else {
  
            resourcePath = THREE.LoaderUtils.extractUrlBase(url);
  
          }
  
          // Tells the LoadingManager to track an extra item, which resolves after
          // the model is fully loaded. This means the count of items loaded will
          // be incorrect, but ensures manager.onLoad() does not fire early.
          scope.manager.itemStart(url);
  
          var _onError = function (e) {
  
            if (onError) {
  
              onError(e);
  
            } else {
  
              console.error(e);
  
            }
  
            scope.manager.itemError(url);
            scope.manager.itemEnd(url);
  
          };
  
          var loader = new THREE.FileLoader(scope.manager);
  
          loader.setPath(this.path);
          loader.setResponseType('arraybuffer');
  
          if (scope.crossOrigin === 'use-credentials') {
  
            loader.setWithCredentials(true);
  
          }
  
          loader.load(url, function (data) {
  
            try {
  
              scope.parse(data, resourcePath, function (gltf) {
  
                onLoad(gltf);
  
                scope.manager.itemEnd(url);
  
              }, _onError);
  
            } catch (e) {
  
              _onError(e);
  
            }
  
          }, onProgress, _onError);
  
        },
  
        setCrossOrigin: function (value) {
  
          this.crossOrigin = value;
          return this;
  
        },
  
        setPath: function (value) {
  
          this.path = value;
          return this;
  
        },
  
        setResourcePath: function (value) {
  
          this.resourcePath = value;
          return this;
  
        },
  
        setDRACOLoader: function (dracoLoader) {
  
          this.dracoLoader = dracoLoader;
          return this;
  
        },
  
        setDDSLoader: function (ddsLoader) {
  
          this.ddsLoader = ddsLoader;
          return this;
  
        },
  
        parse: function (data, path, onLoad, onError) {
  
          var content;
          var extensions = {};
  
          if (typeof data === 'string') {
  
            content = data;
  
          } else {
  
            var magic = THREE.LoaderUtils.decodeText(new Uint8Array(data, 0, 4));
  
            if (magic === BINARY_EXTENSION_HEADER_MAGIC) {
  
              try {
  
                extensions[EXTENSIONS.KHR_BINARY_GLTF] = new GLTFBinaryExtension(data);
  
              } catch (error) {
  
                if (onError) onError(error);
                return;
  
              }
  
              content = extensions[EXTENSIONS.KHR_BINARY_GLTF].content;
  
            } else {
  
              content = THREE.LoaderUtils.decodeText(new Uint8Array(data));
  
            }
  
          }
  
          var json = JSON.parse(content);
  
          if (json.asset === undefined || json.asset.version[0] < 2) {
  
            if (onError) onError(new Error('THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported. Use LegacyGLTFLoader instead.'));
            return;
  
          }
  
          if (json.extensionsUsed) {
  
            for (var i = 0; i < json.extensionsUsed.length; ++i) {
  
              var extensionName = json.extensionsUsed[i];
              var extensionsRequired = json.extensionsRequired || [];
  
              switch (extensionName) {
  
                case EXTENSIONS.KHR_LIGHTS_PUNCTUAL:
                  extensions[extensionName] = new GLTFLightsExtension(json);
                  break;
  
                case EXTENSIONS.KHR_MATERIALS_UNLIT:
                  extensions[extensionName] = new GLTFMaterialsUnlitExtension();
                  break;
  
                case EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS:
                  extensions[extensionName] = new GLTFMaterialsPbrSpecularGlossinessExtension();
                  break;
  
                case EXTENSIONS.KHR_DRACO_MESH_COMPRESSION:
                  extensions[extensionName] = new GLTFDracoMeshCompressionExtension(json, this.dracoLoader);
                  break;
  
                case EXTENSIONS.MSFT_TEXTURE_DDS:
                  extensions[EXTENSIONS.MSFT_TEXTURE_DDS] = new GLTFTextureDDSExtension(this.ddsLoader);
                  break;
  
                case EXTENSIONS.KHR_TEXTURE_TRANSFORM:
                  extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM] = new GLTFTextureTransformExtension();
                  break;
  
                default:
  
                  if (extensionsRequired.indexOf(extensionName) >= 0) {
  
                    console.warn('THREE.GLTFLoader: Unknown extension "' + extensionName + '".');
  
                  }
  
              }
  
            }
  
          }
  
          var parser = new GLTFParser(json, extensions, {
  
            path: path || this.resourcePath || '',
            crossOrigin: this.crossOrigin,
            manager: this.manager
  
          });
  
          parser.parse(onLoad, onError);
  
        }
  
      };
  
      /* GLTFREGISTRY */
  
      function GLTFRegistry() {
  
        var objects = {};
  
        return {
  
          get: function (key) {
  
            return objects[key];
  
          },
  
          add: function (key, object) {
  
            objects[key] = object;
  
          },
  
          remove: function (key) {
  
            delete objects[key];
  
          },
  
          removeAll: function () {
  
            objects = {};
  
          }
  
        };
  
      }
  
      /*********************************/
      /********** EXTENSIONS ***********/
      /*********************************/
  
      var EXTENSIONS = {
        KHR_BINARY_GLTF: 'KHR_binary_glTF',
        KHR_DRACO_MESH_COMPRESSION: 'KHR_draco_mesh_compression',
        KHR_LIGHTS_PUNCTUAL: 'KHR_lights_punctual',
        KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS: 'KHR_materials_pbrSpecularGlossiness',
        KHR_MATERIALS_UNLIT: 'KHR_materials_unlit',
        KHR_TEXTURE_TRANSFORM: 'KHR_texture_transform',
        MSFT_TEXTURE_DDS: 'MSFT_texture_dds'
      };
  
      /**
       * DDS Texture Extension
       *
       * Specification:
       * https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/MSFT_texture_dds
       *
       */
      function GLTFTextureDDSExtension(ddsLoader) {
  
        if (!ddsLoader) {
  
          throw new Error('THREE.GLTFLoader: Attempting to load .dds texture without importing THREE.DDSLoader');
  
        }
  
        this.name = EXTENSIONS.MSFT_TEXTURE_DDS;
        this.ddsLoader = ddsLoader;
  
      }
  
      /**
       * Lights Extension
       *
       * Specification: PENDING
       */
      function GLTFLightsExtension(json) {
  
        this.name = EXTENSIONS.KHR_LIGHTS_PUNCTUAL;
  
        var extension = (json.extensions && json.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL]) || {};
        this.lightDefs = extension.lights || [];
  
      }
  
      GLTFLightsExtension.prototype.loadLight = function (lightIndex) {
  
        var lightDef = this.lightDefs[lightIndex];
        var lightNode;
  
        var color = new THREE.Color(0xffffff);
        if (lightDef.color !== undefined) color.fromArray(lightDef.color);
  
        var range = lightDef.range !== undefined ? lightDef.range : 0;
  
        switch (lightDef.type) {
  
          case 'directional':
            lightNode = new THREE.DirectionalLight(color);
            lightNode.target.position.set(0, 0, - 1);
            lightNode.add(lightNode.target);
            break;
  
          case 'point':
            lightNode = new THREE.PointLight(color);
            lightNode.distance = range;
            break;
  
          case 'spot':
            lightNode = new THREE.SpotLight(color);
            lightNode.distance = range;
            // Handle spotlight properties.
            lightDef.spot = lightDef.spot || {};
            lightDef.spot.innerConeAngle = lightDef.spot.innerConeAngle !== undefined ? lightDef.spot.innerConeAngle : 0;
            lightDef.spot.outerConeAngle = lightDef.spot.outerConeAngle !== undefined ? lightDef.spot.outerConeAngle : Math.PI / 4.0;
            lightNode.angle = lightDef.spot.outerConeAngle;
            lightNode.penumbra = 1.0 - lightDef.spot.innerConeAngle / lightDef.spot.outerConeAngle;
            lightNode.target.position.set(0, 0, - 1);
            lightNode.add(lightNode.target);
            break;
  
          default:
            throw new Error('THREE.GLTFLoader: Unexpected light type, "' + lightDef.type + '".');
  
        }
  
        // Some lights (e.g. spot) default to a position other than the origin. Reset the position
        // here, because node-level parsing will only override position if explicitly specified.
        lightNode.position.set(0, 0, 0);
  
        lightNode.decay = 2;
  
        if (lightDef.intensity !== undefined) lightNode.intensity = lightDef.intensity;
  
        lightNode.name = lightDef.name || ('light_' + lightIndex);
  
        return Promise.resolve(lightNode);
  
      };
  
      /**
       * Unlit Materials Extension (pending)
       *
       * PR: https://github.com/KhronosGroup/glTF/pull/1163
       */
      function GLTFMaterialsUnlitExtension() {
  
        this.name = EXTENSIONS.KHR_MATERIALS_UNLIT;
  
      }
  
      GLTFMaterialsUnlitExtension.prototype.getMaterialType = function () {
  
        return THREE.MeshBasicMaterial;
  
      };
  
      GLTFMaterialsUnlitExtension.prototype.extendParams = function (materialParams, materialDef, parser) {
  
        var pending = [];
  
        materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
        materialParams.opacity = 1.0;
  
        var metallicRoughness = materialDef.pbrMetallicRoughness;
  
        if (metallicRoughness) {
  
          if (Array.isArray(metallicRoughness.baseColorFactor)) {
  
            var array = metallicRoughness.baseColorFactor;
  
            materialParams.color.fromArray(array);
            materialParams.opacity = array[3];
  
          }
  
          if (metallicRoughness.baseColorTexture !== undefined) {
  
            pending.push(parser.assignTexture(materialParams, 'map', metallicRoughness.baseColorTexture));
  
          }
  
        }
  
        return Promise.all(pending);
  
      };
  
      /* BINARY EXTENSION */
      var BINARY_EXTENSION_HEADER_MAGIC = 'glTF';
      var BINARY_EXTENSION_HEADER_LENGTH = 12;
      var BINARY_EXTENSION_CHUNK_TYPES = { JSON: 0x4E4F534A, BIN: 0x004E4942 };
  
      function GLTFBinaryExtension(data) {
  
        this.name = EXTENSIONS.KHR_BINARY_GLTF;
        this.content = null;
        this.body = null;
  
        var headerView = new DataView(data, 0, BINARY_EXTENSION_HEADER_LENGTH);
  
        this.header = {
          magic: THREE.LoaderUtils.decodeText(new Uint8Array(data.slice(0, 4))),
          version: headerView.getUint32(4, true),
          length: headerView.getUint32(8, true)
        };
  
        if (this.header.magic !== BINARY_EXTENSION_HEADER_MAGIC) {
  
          throw new Error('THREE.GLTFLoader: Unsupported glTF-Binary header.');
  
        } else if (this.header.version < 2.0) {
  
          throw new Error('THREE.GLTFLoader: Legacy binary file detected. Use LegacyGLTFLoader instead.');
  
        }
  
        var chunkView = new DataView(data, BINARY_EXTENSION_HEADER_LENGTH);
        var chunkIndex = 0;
  
        while (chunkIndex < chunkView.byteLength) {
  
          var chunkLength = chunkView.getUint32(chunkIndex, true);
          chunkIndex += 4;
  
          var chunkType = chunkView.getUint32(chunkIndex, true);
          chunkIndex += 4;
  
          if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.JSON) {
  
            var contentArray = new Uint8Array(data, BINARY_EXTENSION_HEADER_LENGTH + chunkIndex, chunkLength);
            this.content = THREE.LoaderUtils.decodeText(contentArray);
  
          } else if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.BIN) {
  
            var byteOffset = BINARY_EXTENSION_HEADER_LENGTH + chunkIndex;
            this.body = data.slice(byteOffset, byteOffset + chunkLength);
  
          }
  
          // Clients must ignore chunks with unknown types.
  
          chunkIndex += chunkLength;
  
        }
  
        if (this.content === null) {
  
          throw new Error('THREE.GLTFLoader: JSON content not found.');
  
        }
  
      }
  
      /**
       * DRACO Mesh Compression Extension
       *
       * Specification: https://github.com/KhronosGroup/glTF/pull/874
       */
      function GLTFDracoMeshCompressionExtension(json, dracoLoader) {
  
        if (!dracoLoader) {
  
          throw new Error('THREE.GLTFLoader: No DRACOLoader instance provided.');
  
        }
  
        this.name = EXTENSIONS.KHR_DRACO_MESH_COMPRESSION;
        this.json = json;
        this.dracoLoader = dracoLoader;
  
      }
  
      GLTFDracoMeshCompressionExtension.prototype.decodePrimitive = function (primitive, parser) {
  
        var json = this.json;
        var dracoLoader = this.dracoLoader;
        var bufferViewIndex = primitive.extensions[this.name].bufferView;
        var gltfAttributeMap = primitive.extensions[this.name].attributes;
        var threeAttributeMap = {};
        var attributeNormalizedMap = {};
        var attributeTypeMap = {};
  
        for (var attributeName in gltfAttributeMap) {
  
          var threeAttributeName = ATTRIBUTES[attributeName] || attributeName.toLowerCase();
  
          threeAttributeMap[threeAttributeName] = gltfAttributeMap[attributeName];
  
        }
  
        for (attributeName in primitive.attributes) {
  
          var threeAttributeName = ATTRIBUTES[attributeName] || attributeName.toLowerCase();
  
          if (gltfAttributeMap[attributeName] !== undefined) {
  
            var accessorDef = json.accessors[primitive.attributes[attributeName]];
            var componentType = WEBGL_COMPONENT_TYPES[accessorDef.componentType];
  
            attributeTypeMap[threeAttributeName] = componentType;
            attributeNormalizedMap[threeAttributeName] = accessorDef.normalized === true;
  
          }
  
        }
  
        return parser.getDependency('bufferView', bufferViewIndex).then(function (bufferView) {
  
          return new Promise(function (resolve) {
  
            dracoLoader.decodeDracoFile(bufferView, function (geometry) {
  
              for (var attributeName in geometry.attributes) {
  
                var attribute = geometry.attributes[attributeName];
                var normalized = attributeNormalizedMap[attributeName];
  
                if (normalized !== undefined) attribute.normalized = normalized;
  
              }
  
              resolve(geometry);
  
            }, threeAttributeMap, attributeTypeMap);
  
          });
  
        });
  
      };
  
      /**
       * Texture Transform Extension
       *
       * Specification:
       */
      function GLTFTextureTransformExtension() {
  
        this.name = EXTENSIONS.KHR_TEXTURE_TRANSFORM;
  
      }
  
      GLTFTextureTransformExtension.prototype.extendTexture = function (texture, transform) {
  
        texture = texture.clone();
  
        if (transform.offset !== undefined) {
  
          texture.offset.fromArray(transform.offset);
  
        }
  
        if (transform.rotation !== undefined) {
  
          texture.rotation = transform.rotation;
  
        }
  
        if (transform.scale !== undefined) {
  
          texture.repeat.fromArray(transform.scale);
  
        }
  
        if (transform.texCoord !== undefined) {
  
          console.warn('THREE.GLTFLoader: Custom UV sets in "' + this.name + '" extension not yet supported.');
  
        }
  
        texture.needsUpdate = true;
  
        return texture;
  
      };
  
      /**
       * Specular-Glossiness Extension
       *
       * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_pbrSpecularGlossiness
       */
      function GLTFMaterialsPbrSpecularGlossinessExtension() {
  
        return {
  
          name: EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS,
  
          specularGlossinessParams: [
            'color',
            'map',
            'lightMap',
            'lightMapIntensity',
            'aoMap',
            'aoMapIntensity',
            'emissive',
            'emissiveIntensity',
            'emissiveMap',
            'bumpMap',
            'bumpScale',
            'normalMap',
            'displacementMap',
            'displacementScale',
            'displacementBias',
            'specularMap',
            'specular',
            'glossinessMap',
            'glossiness',
            'alphaMap',
            'envMap',
            'envMapIntensity',
            'refractionRatio',
          ],
  
          getMaterialType: function () {
  
            return THREE.ShaderMaterial;
  
          },
  
          extendParams: function (materialParams, materialDef, parser) {
  
            var pbrSpecularGlossiness = materialDef.extensions[this.name];
  
            var shader = THREE.ShaderLib['standard'];
  
            var uniforms = THREE.UniformsUtils.clone(shader.uniforms);
  
            var specularMapParsFragmentChunk = [
              '#ifdef USE_SPECULARMAP',
              '	uniform sampler2D specularMap;',
              '#endif'
            ].join('\n');
  
            var glossinessMapParsFragmentChunk = [
              '#ifdef USE_GLOSSINESSMAP',
              '	uniform sampler2D glossinessMap;',
              '#endif'
            ].join('\n');
  
            var specularMapFragmentChunk = [
              'vec3 specularFactor = specular;',
              '#ifdef USE_SPECULARMAP',
              '	vec4 texelSpecular = texture2D( specularMap, vUv );',
              '	texelSpecular = sRGBToLinear( texelSpecular );',
              '	// reads channel RGB, compatible with a glTF Specular-Glossiness (RGBA) texture',
              '	specularFactor *= texelSpecular.rgb;',
              '#endif'
            ].join('\n');
  
            var glossinessMapFragmentChunk = [
              'float glossinessFactor = glossiness;',
              '#ifdef USE_GLOSSINESSMAP',
              '	vec4 texelGlossiness = texture2D( glossinessMap, vUv );',
              '	// reads channel A, compatible with a glTF Specular-Glossiness (RGBA) texture',
              '	glossinessFactor *= texelGlossiness.a;',
              '#endif'
            ].join('\n');
  
            var lightPhysicalFragmentChunk = [
              'PhysicalMaterial material;',
              'material.diffuseColor = diffuseColor.rgb;',
              'material.specularRoughness = clamp( 1.0 - glossinessFactor, 0.04, 1.0 );',
              'material.specularColor = specularFactor.rgb;',
            ].join('\n');
  
            var fragmentShader = shader.fragmentShader
              .replace('uniform float roughness;', 'uniform vec3 specular;')
              .replace('uniform float metalness;', 'uniform float glossiness;')
              .replace('#include <roughnessmap_pars_fragment>', specularMapParsFragmentChunk)
              .replace('#include <metalnessmap_pars_fragment>', glossinessMapParsFragmentChunk)
              .replace('#include <roughnessmap_fragment>', specularMapFragmentChunk)
              .replace('#include <metalnessmap_fragment>', glossinessMapFragmentChunk)
              .replace('#include <lights_physical_fragment>', lightPhysicalFragmentChunk);
  
            delete uniforms.roughness;
            delete uniforms.metalness;
            delete uniforms.roughnessMap;
            delete uniforms.metalnessMap;
  
            uniforms.specular = { value: new THREE.Color().setHex(0x111111) };
            uniforms.glossiness = { value: 0.5 };
            uniforms.specularMap = { value: null };
            uniforms.glossinessMap = { value: null };
  
            materialParams.vertexShader = shader.vertexShader;
            materialParams.fragmentShader = fragmentShader;
            materialParams.uniforms = uniforms;
            materialParams.defines = { 'STANDARD': '' }
  
            materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
            materialParams.opacity = 1.0;
  
            var pending = [];
  
            if (Array.isArray(pbrSpecularGlossiness.diffuseFactor)) {
  
              var array = pbrSpecularGlossiness.diffuseFactor;
  
              materialParams.color.fromArray(array);
              materialParams.opacity = array[3];
  
            }
  
            if (pbrSpecularGlossiness.diffuseTexture !== undefined) {
  
              pending.push(parser.assignTexture(materialParams, 'map', pbrSpecularGlossiness.diffuseTexture));
  
            }
  
            materialParams.emissive = new THREE.Color(0.0, 0.0, 0.0);
            materialParams.glossiness = pbrSpecularGlossiness.glossinessFactor !== undefined ? pbrSpecularGlossiness.glossinessFactor : 1.0;
            materialParams.specular = new THREE.Color(1.0, 1.0, 1.0);
  
            if (Array.isArray(pbrSpecularGlossiness.specularFactor)) {
  
              materialParams.specular.fromArray(pbrSpecularGlossiness.specularFactor);
  
            }
  
            if (pbrSpecularGlossiness.specularGlossinessTexture !== undefined) {
  
              var specGlossMapDef = pbrSpecularGlossiness.specularGlossinessTexture;
              pending.push(parser.assignTexture(materialParams, 'glossinessMap', specGlossMapDef));
              pending.push(parser.assignTexture(materialParams, 'specularMap', specGlossMapDef));
  
            }
  
            return Promise.all(pending);
  
          },
  
          createMaterial: function (params) {
  
            // setup material properties based on MeshStandardMaterial for Specular-Glossiness
  
            var material = new THREE.ShaderMaterial({
              defines: params.defines,
              vertexShader: params.vertexShader,
              fragmentShader: params.fragmentShader,
              uniforms: params.uniforms,
              fog: true,
              lights: true,
              opacity: params.opacity,
              transparent: params.transparent
            });
  
            material.isGLTFSpecularGlossinessMaterial = true;
  
            material.color = params.color;
  
            material.map = params.map === undefined ? null : params.map;
  
            material.lightMap = null;
            material.lightMapIntensity = 1.0;
  
            material.aoMap = params.aoMap === undefined ? null : params.aoMap;
            material.aoMapIntensity = 1.0;
  
            material.emissive = params.emissive;
            material.emissiveIntensity = 1.0;
            material.emissiveMap = params.emissiveMap === undefined ? null : params.emissiveMap;
  
            material.bumpMap = params.bumpMap === undefined ? null : params.bumpMap;
            material.bumpScale = 1;
  
            material.normalMap = params.normalMap === undefined ? null : params.normalMap;
  
            if (params.normalScale) material.normalScale = params.normalScale;
  
            material.displacementMap = null;
            material.displacementScale = 1;
            material.displacementBias = 0;
  
            material.specularMap = params.specularMap === undefined ? null : params.specularMap;
            material.specular = params.specular;
  
            material.glossinessMap = params.glossinessMap === undefined ? null : params.glossinessMap;
            material.glossiness = params.glossiness;
  
            material.alphaMap = null;
  
            material.envMap = params.envMap === undefined ? null : params.envMap;
            material.envMapIntensity = 1.0;
  
            material.refractionRatio = 0.98;
  
            material.extensions.derivatives = true;
  
            return material;
  
          },
  
          /**
           * Clones a GLTFSpecularGlossinessMaterial instance. The ShaderMaterial.copy() method can
           * copy only properties it knows about or inherits, and misses many properties that would
           * normally be defined by MeshStandardMaterial.
           *
           * This method allows GLTFSpecularGlossinessMaterials to be cloned in the process of
           * loading a glTF model, but cloning later (e.g. by the user) would require these changes
           * AND also updating `.onBeforeRender` on the parent mesh.
           *
           * @param  {THREE.ShaderMaterial} source
           * @return {THREE.ShaderMaterial}
           */
          cloneMaterial: function (source) {
  
            var target = source.clone();
  
            target.isGLTFSpecularGlossinessMaterial = true;
  
            var params = this.specularGlossinessParams;
  
            for (var i = 0, il = params.length; i < il; i++) {
  
              var value = source[params[i]];
              target[params[i]] = (value && value.isColor) ? value.clone() : value;
  
            }
  
            return target;
  
          },
  
          // Here's based on refreshUniformsCommon() and refreshUniformsStandard() in WebGLRenderer.
          refreshUniforms: function (renderer, scene, camera, geometry, material) {
  
            if (material.isGLTFSpecularGlossinessMaterial !== true) {
  
              return;
  
            }
  
            var uniforms = material.uniforms;
            var defines = material.defines;
  
            uniforms.opacity.value = material.opacity;
  
            uniforms.diffuse.value.copy(material.color);
            uniforms.emissive.value.copy(material.emissive).multiplyScalar(material.emissiveIntensity);
  
            uniforms.map.value = material.map;
            uniforms.specularMap.value = material.specularMap;
            uniforms.alphaMap.value = material.alphaMap;
  
            uniforms.lightMap.value = material.lightMap;
            uniforms.lightMapIntensity.value = material.lightMapIntensity;
  
            uniforms.aoMap.value = material.aoMap;
            uniforms.aoMapIntensity.value = material.aoMapIntensity;
  
            // uv repeat and offset setting priorities
            // 1. color map
            // 2. specular map
            // 3. normal map
            // 4. bump map
            // 5. alpha map
            // 6. emissive map
  
            var uvScaleMap;
  
            if (material.map) {
  
              uvScaleMap = material.map;
  
            } else if (material.specularMap) {
  
              uvScaleMap = material.specularMap;
  
            } else if (material.displacementMap) {
  
              uvScaleMap = material.displacementMap;
  
            } else if (material.normalMap) {
  
              uvScaleMap = material.normalMap;
  
            } else if (material.bumpMap) {
  
              uvScaleMap = material.bumpMap;
  
            } else if (material.glossinessMap) {
  
              uvScaleMap = material.glossinessMap;
  
            } else if (material.alphaMap) {
  
              uvScaleMap = material.alphaMap;
  
            } else if (material.emissiveMap) {
  
              uvScaleMap = material.emissiveMap;
  
            }
  
            if (uvScaleMap !== undefined) {
  
              // backwards compatibility
              if (uvScaleMap.isWebGLRenderTarget) {
  
                uvScaleMap = uvScaleMap.texture;
  
              }
  
              if (uvScaleMap.matrixAutoUpdate === true) {
  
                uvScaleMap.updateMatrix();
  
              }
  
              uniforms.uvTransform.value.copy(uvScaleMap.matrix);
  
            }
  
            if (material.envMap) {
  
              uniforms.envMap.value = material.envMap;
              uniforms.envMapIntensity.value = material.envMapIntensity;
  
              // don't flip CubeTexture envMaps, flip everything else:
              //  WebGLRenderTargetCube will be flipped for backwards compatibility
              //  WebGLRenderTargetCube.texture will be flipped because it's a Texture and NOT a CubeTexture
              // this check must be handled differently, or removed entirely, if WebGLRenderTargetCube uses a CubeTexture in the future
              uniforms.flipEnvMap.value = material.envMap.isCubeTexture ? - 1 : 1;
  
              uniforms.reflectivity.value = material.reflectivity;
              uniforms.refractionRatio.value = material.refractionRatio;
  
              uniforms.maxMipLevel.value = renderer.properties.get(material.envMap).__maxMipLevel;
  
            }
  
            uniforms.specular.value.copy(material.specular);
            uniforms.glossiness.value = material.glossiness;
  
            uniforms.glossinessMap.value = material.glossinessMap;
  
            uniforms.emissiveMap.value = material.emissiveMap;
            uniforms.bumpMap.value = material.bumpMap;
            uniforms.normalMap.value = material.normalMap;
  
            uniforms.displacementMap.value = material.displacementMap;
            uniforms.displacementScale.value = material.displacementScale;
            uniforms.displacementBias.value = material.displacementBias;
  
            if (uniforms.glossinessMap.value !== null && defines.USE_GLOSSINESSMAP === undefined) {
  
              defines.USE_GLOSSINESSMAP = '';
              // set USE_ROUGHNESSMAP to enable vUv
              defines.USE_ROUGHNESSMAP = '';
  
            }
  
            if (uniforms.glossinessMap.value === null && defines.USE_GLOSSINESSMAP !== undefined) {
  
              delete defines.USE_GLOSSINESSMAP;
              delete defines.USE_ROUGHNESSMAP;
  
            }
  
          }
  
        };
  
      }
  
      /*********************************/
      /********** INTERPOLATION ********/
      /*********************************/
  
      // Spline Interpolation
      // Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#appendix-c-spline-interpolation
      function GLTFCubicSplineInterpolant(parameterPositions, sampleValues, sampleSize, resultBuffer) {
  
        THREE.Interpolant.call(this, parameterPositions, sampleValues, sampleSize, resultBuffer);
  
      }
  
      GLTFCubicSplineInterpolant.prototype = Object.create(THREE.Interpolant.prototype);
      GLTFCubicSplineInterpolant.prototype.constructor = GLTFCubicSplineInterpolant;
  
      GLTFCubicSplineInterpolant.prototype.copySampleValue_ = function (index) {
  
        // Copies a sample value to the result buffer. See description of glTF
        // CUBICSPLINE values layout in interpolate_() function below.
  
        var result = this.resultBuffer,
          values = this.sampleValues,
          valueSize = this.valueSize,
          offset = index * valueSize * 3 + valueSize;
  
        for (var i = 0; i !== valueSize; i++) {
  
          result[i] = values[offset + i];
  
        }
  
        return result;
  
      };
  
      GLTFCubicSplineInterpolant.prototype.beforeStart_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;
  
      GLTFCubicSplineInterpolant.prototype.afterEnd_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;
  
      GLTFCubicSplineInterpolant.prototype.interpolate_ = function (i1, t0, t, t1) {
  
        var result = this.resultBuffer;
        var values = this.sampleValues;
        var stride = this.valueSize;
  
        var stride2 = stride * 2;
        var stride3 = stride * 3;
  
        var td = t1 - t0;
  
        var p = (t - t0) / td;
        var pp = p * p;
        var ppp = pp * p;
  
        var offset1 = i1 * stride3;
        var offset0 = offset1 - stride3;
  
        var s2 = - 2 * ppp + 3 * pp;
        var s3 = ppp - pp;
        var s0 = 1 - s2;
        var s1 = s3 - pp + p;
  
        // Layout of keyframe output values for CUBICSPLINE animations:
        //   [ inTangent_1, splineVertex_1, outTangent_1, inTangent_2, splineVertex_2, ... ]
        for (var i = 0; i !== stride; i++) {
  
          var p0 = values[offset0 + i + stride]; // splineVertex_k
          var m0 = values[offset0 + i + stride2] * td; // outTangent_k * (t_k+1 - t_k)
          var p1 = values[offset1 + i + stride]; // splineVertex_k+1
          var m1 = values[offset1 + i] * td; // inTangent_k+1 * (t_k+1 - t_k)
  
          result[i] = s0 * p0 + s1 * m0 + s2 * p1 + s3 * m1;
  
        }
  
        return result;
  
      };
  
      /*********************************/
      /********** INTERNALS ************/
      /*********************************/
  
      /* CONSTANTS */
  
      var WEBGL_CONSTANTS = {
        FLOAT: 5126,
        //FLOAT_MAT2: 35674,
        FLOAT_MAT3: 35675,
        FLOAT_MAT4: 35676,
        FLOAT_VEC2: 35664,
        FLOAT_VEC3: 35665,
        FLOAT_VEC4: 35666,
        LINEAR: 9729,
        REPEAT: 10497,
        SAMPLER_2D: 35678,
        POINTS: 0,
        LINES: 1,
        LINE_LOOP: 2,
        LINE_STRIP: 3,
        TRIANGLES: 4,
        TRIANGLE_STRIP: 5,
        TRIANGLE_FAN: 6,
        UNSIGNED_BYTE: 5121,
        UNSIGNED_SHORT: 5123
      };
  
      var WEBGL_COMPONENT_TYPES = {
        5120: Int8Array,
        5121: Uint8Array,
        5122: Int16Array,
        5123: Uint16Array,
        5125: Uint32Array,
        5126: Float32Array
      };
  
      var WEBGL_FILTERS = {
        9728: THREE.NearestFilter,
        9729: THREE.LinearFilter,
        9984: THREE.NearestMipmapNearestFilter,
        9985: THREE.LinearMipmapNearestFilter,
        9986: THREE.NearestMipmapLinearFilter,
        9987: THREE.LinearMipmapLinearFilter
      };
  
      var WEBGL_WRAPPINGS = {
        33071: THREE.ClampToEdgeWrapping,
        33648: THREE.MirroredRepeatWrapping,
        10497: THREE.RepeatWrapping
      };
  
      var WEBGL_TYPE_SIZES = {
        'SCALAR': 1,
        'VEC2': 2,
        'VEC3': 3,
        'VEC4': 4,
        'MAT2': 4,
        'MAT3': 9,
        'MAT4': 16
      };
  
      var ATTRIBUTES = {
        POSITION: 'position',
        NORMAL: 'normal',
        TANGENT: 'tangent',
        TEXCOORD_0: 'uv',
        TEXCOORD_1: 'uv2',
        COLOR_0: 'color',
        WEIGHTS_0: 'skinWeight',
        JOINTS_0: 'skinIndex',
      };
  
      var PATH_PROPERTIES = {
        scale: 'scale',
        translation: 'position',
        rotation: 'quaternion',
        weights: 'morphTargetInfluences'
      };
  
      var INTERPOLATION = {
        CUBICSPLINE: undefined, // We use a custom interpolant (GLTFCubicSplineInterpolation) for CUBICSPLINE tracks. Each
        // keyframe track will be initialized with a default interpolation type, then modified.
        LINEAR: THREE.InterpolateLinear,
        STEP: THREE.InterpolateDiscrete
      };
  
      var ALPHA_MODES = {
        OPAQUE: 'OPAQUE',
        MASK: 'MASK',
        BLEND: 'BLEND'
      };
  
      var MIME_TYPE_FORMATS = {
        'image/png': THREE.RGBAFormat,
        'image/jpeg': THREE.RGBFormat
      };
  
      /* UTILITY FUNCTIONS */
  
      function resolveURL(url, path) {
  
        // Invalid URL
        if (typeof url !== 'string' || url === '') return '';
  
        // Host Relative URL
        if (/^https?:\/\//i.test(path) && /^\//.test(url)) {
  
          path = path.replace(/(^https?:\/\/[^\/]+).*/i, '$1');
  
        }
  
        // Absolute URL http://,https://,//
        if (/^(https?:)?\/\//i.test(url)) return url;
  
        // Data URI
        if (/^data:.*,.*$/i.test(url)) return url;
  
        // Blob URL
        if (/^blob:.*$/i.test(url)) return url;
  
        // Relative URL
        return path + url;
  
      }
  
      var defaultMaterial;
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#default-material
       */
      function createDefaultMaterial() {
  
        defaultMaterial = defaultMaterial || new THREE.MeshStandardMaterial({
          color: 0xFFFFFF,
          emissive: 0x000000,
          metalness: 1,
          roughness: 1,
          transparent: false,
          depthTest: true,
          side: THREE.FrontSide
        });
  
        return defaultMaterial;
  
      }
  
      function addUnknownExtensionsToUserData(knownExtensions, object, objectDef) {
  
        // Add unknown glTF extensions to an object's userData.
  
        for (var name in objectDef.extensions) {
  
          if (knownExtensions[name] === undefined) {
  
            object.userData.gltfExtensions = object.userData.gltfExtensions || {};
            object.userData.gltfExtensions[name] = objectDef.extensions[name];
  
          }
  
        }
  
      }
  
      /**
       * @param {THREE.Object3D|THREE.Material|THREE.BufferGeometry} object
       * @param {GLTF.definition} gltfDef
       */
      function assignExtrasToUserData(object, gltfDef) {
  
        if (gltfDef.extras !== undefined) {
  
          if (typeof gltfDef.extras === 'object') {
  
            Object.assign(object.userData, gltfDef.extras);
  
          } else {
  
            console.warn('THREE.GLTFLoader: Ignoring primitive type .extras, ' + gltfDef.extras);
  
          }
  
        }
  
      }
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#morph-targets
       *
       * @param {THREE.BufferGeometry} geometry
       * @param {Array<GLTF.Target>} targets
       * @param {GLTFParser} parser
       * @return {Promise<THREE.BufferGeometry>}
       */
      function addMorphTargets(geometry, targets, parser) {
  
        var hasMorphPosition = false;
        var hasMorphNormal = false;
  
        for (var i = 0, il = targets.length; i < il; i++) {
  
          var target = targets[i];
  
          if (target.POSITION !== undefined) hasMorphPosition = true;
          if (target.NORMAL !== undefined) hasMorphNormal = true;
  
          if (hasMorphPosition && hasMorphNormal) break;
  
        }
  
        if (!hasMorphPosition && !hasMorphNormal) return Promise.resolve(geometry);
  
        var pendingPositionAccessors = [];
        var pendingNormalAccessors = [];
  
        for (var i = 0, il = targets.length; i < il; i++) {
  
          var target = targets[i];
  
          if (hasMorphPosition) {
  
            var pendingAccessor = target.POSITION !== undefined
              ? parser.getDependency('accessor', target.POSITION)
              : geometry.attributes.position;
  
            pendingPositionAccessors.push(pendingAccessor);
  
          }
  
          if (hasMorphNormal) {
  
            var pendingAccessor = target.NORMAL !== undefined
              ? parser.getDependency('accessor', target.NORMAL)
              : geometry.attributes.normal;
  
            pendingNormalAccessors.push(pendingAccessor);
  
          }
  
        }
  
        return Promise.all([
          Promise.all(pendingPositionAccessors),
          Promise.all(pendingNormalAccessors)
        ]).then(function (accessors) {
  
          var morphPositions = accessors[0];
          var morphNormals = accessors[1];
  
          // Clone morph target accessors before modifying them.
  
          for (var i = 0, il = morphPositions.length; i < il; i++) {
  
            if (geometry.attributes.position === morphPositions[i]) continue;
  
            morphPositions[i] = cloneBufferAttribute(morphPositions[i]);
  
          }
  
          for (var i = 0, il = morphNormals.length; i < il; i++) {
  
            if (geometry.attributes.normal === morphNormals[i]) continue;
  
            morphNormals[i] = cloneBufferAttribute(morphNormals[i]);
  
          }
  
          for (var i = 0, il = targets.length; i < il; i++) {
  
            var target = targets[i];
            var attributeName = 'morphTarget' + i;
  
            if (hasMorphPosition) {
  
              // Three.js morph position is absolute value. The formula is
              //   basePosition
              //     + weight0 * ( morphPosition0 - basePosition )
              //     + weight1 * ( morphPosition1 - basePosition )
              //     ...
              // while the glTF one is relative
              //   basePosition
              //     + weight0 * glTFmorphPosition0
              //     + weight1 * glTFmorphPosition1
              //     ...
              // then we need to convert from relative to absolute here.
  
              if (target.POSITION !== undefined) {
  
                var positionAttribute = morphPositions[i];
                positionAttribute.name = attributeName;
  
                var position = geometry.attributes.position;
  
                for (var j = 0, jl = positionAttribute.count; j < jl; j++) {
  
                  positionAttribute.setXYZ(
                    j,
                    positionAttribute.getX(j) + position.getX(j),
                    positionAttribute.getY(j) + position.getY(j),
                    positionAttribute.getZ(j) + position.getZ(j)
                  );
  
                }
  
              }
  
            }
  
            if (hasMorphNormal) {
  
              // see target.POSITION's comment
  
              if (target.NORMAL !== undefined) {
  
                var normalAttribute = morphNormals[i];
                normalAttribute.name = attributeName;
  
                var normal = geometry.attributes.normal;
  
                for (var j = 0, jl = normalAttribute.count; j < jl; j++) {
  
                  normalAttribute.setXYZ(
                    j,
                    normalAttribute.getX(j) + normal.getX(j),
                    normalAttribute.getY(j) + normal.getY(j),
                    normalAttribute.getZ(j) + normal.getZ(j)
                  );
  
                }
  
              }
  
            }
  
          }
  
          if (hasMorphPosition) geometry.morphAttributes.position = morphPositions;
          if (hasMorphNormal) geometry.morphAttributes.normal = morphNormals;
  
          return geometry;
  
        });
  
      }
  
      /**
       * @param {THREE.Mesh} mesh
       * @param {GLTF.Mesh} meshDef
       */
      function updateMorphTargets(mesh, meshDef) {
  
        mesh.updateMorphTargets();
  
        if (meshDef.weights !== undefined) {
  
          for (var i = 0, il = meshDef.weights.length; i < il; i++) {
  
            mesh.morphTargetInfluences[i] = meshDef.weights[i];
  
          }
  
        }
  
        // .extras has user-defined data, so check that .extras.targetNames is an array.
        if (meshDef.extras && Array.isArray(meshDef.extras.targetNames)) {
  
          var targetNames = meshDef.extras.targetNames;
  
          if (mesh.morphTargetInfluences.length === targetNames.length) {
  
            mesh.morphTargetDictionary = {};
  
            for (var i = 0, il = targetNames.length; i < il; i++) {
  
              mesh.morphTargetDictionary[targetNames[i]] = i;
  
            }
  
          } else {
  
            console.warn('THREE.GLTFLoader: Invalid extras.targetNames length. Ignoring names.');
  
          }
  
        }
  
      }
  
      function createPrimitiveKey(primitiveDef) {
  
        var dracoExtension = primitiveDef.extensions && primitiveDef.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION];
        var geometryKey;
  
        if (dracoExtension) {
  
          geometryKey = 'draco:' + dracoExtension.bufferView
            + ':' + dracoExtension.indices
            + ':' + createAttributesKey(dracoExtension.attributes);
  
        } else {
  
          geometryKey = primitiveDef.indices + ':' + createAttributesKey(primitiveDef.attributes) + ':' + primitiveDef.mode;
  
        }
  
        return geometryKey;
  
      }
  
      function createAttributesKey(attributes) {
  
        var attributesKey = '';
  
        var keys = Object.keys(attributes).sort();
  
        for (var i = 0, il = keys.length; i < il; i++) {
  
          attributesKey += keys[i] + ':' + attributes[keys[i]] + ';';
  
        }
  
        return attributesKey;
  
      }
  
      function cloneBufferAttribute(attribute) {
  
        if (attribute.isInterleavedBufferAttribute) {
  
          var count = attribute.count;
          var itemSize = attribute.itemSize;
          var array = attribute.array.slice(0, count * itemSize);
  
          for (var i = 0, j = 0; i < count; ++i) {
  
            array[j++] = attribute.getX(i);
            if (itemSize >= 2) array[j++] = attribute.getY(i);
            if (itemSize >= 3) array[j++] = attribute.getZ(i);
            if (itemSize >= 4) array[j++] = attribute.getW(i);
  
          }
  
          return new THREE.BufferAttribute(array, itemSize, attribute.normalized);
  
        }
  
        return attribute.clone();
  
      }
  
      /* GLTF PARSER */
  
      function GLTFParser(json, extensions, options) {
  
        this.json = json || {};
        this.extensions = extensions || {};
        this.options = options || {};
  
        // loader object cache
        this.cache = new GLTFRegistry();
  
        // BufferGeometry caching
        this.primitiveCache = {};
  
        this.textureLoader = new THREE.TextureLoader(this.options.manager);
        this.textureLoader.setCrossOrigin(this.options.crossOrigin);
  
        this.fileLoader = new THREE.FileLoader(this.options.manager);
        this.fileLoader.setResponseType('arraybuffer');
  
        if (this.options.crossOrigin === 'use-credentials') {
  
          this.fileLoader.setWithCredentials(true);
  
        }
  
      }
  
      GLTFParser.prototype.parse = function (onLoad, onError) {
  
        var parser = this;
        var json = this.json;
        var extensions = this.extensions;
  
        // Clear the loader cache
        this.cache.removeAll();
  
        // Mark the special nodes/meshes in json for efficient parse
        this.markDefs();
  
        Promise.all([
  
          this.getDependencies('scene'),
          this.getDependencies('animation'),
          this.getDependencies('camera'),
  
        ]).then(function (dependencies) {
  
          var result = {
            scene: dependencies[0][json.scene || 0],
            scenes: dependencies[0],
            animations: dependencies[1],
            cameras: dependencies[2],
            asset: json.asset,
            parser: parser,
            userData: {}
          };
  
          addUnknownExtensionsToUserData(extensions, result, json);
  
          assignExtrasToUserData(result, json);
  
          onLoad(result);
  
        }).catch(onError);
  
      };
  
      /**
       * Marks the special nodes/meshes in json for efficient parse.
       */
      GLTFParser.prototype.markDefs = function () {
  
        var nodeDefs = this.json.nodes || [];
        var skinDefs = this.json.skins || [];
        var meshDefs = this.json.meshes || [];
  
        var meshReferences = {};
        var meshUses = {};
  
        // Nothing in the node definition indicates whether it is a Bone or an
        // Object3D. Use the skins' joint references to mark bones.
        for (var skinIndex = 0, skinLength = skinDefs.length; skinIndex < skinLength; skinIndex++) {
  
          var joints = skinDefs[skinIndex].joints;
  
          for (var i = 0, il = joints.length; i < il; i++) {
  
            nodeDefs[joints[i]].isBone = true;
  
          }
  
        }
  
        // Meshes can (and should) be reused by multiple nodes in a glTF asset. To
        // avoid having more than one THREE.Mesh with the same name, count
        // references and rename instances below.
        //
        // Example: CesiumMilkTruck sample model reuses "Wheel" meshes.
        for (var nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex++) {
  
          var nodeDef = nodeDefs[nodeIndex];
  
          if (nodeDef.mesh !== undefined) {
  
            if (meshReferences[nodeDef.mesh] === undefined) {
  
              meshReferences[nodeDef.mesh] = meshUses[nodeDef.mesh] = 0;
  
            }
  
            meshReferences[nodeDef.mesh]++;
  
            // Nothing in the mesh definition indicates whether it is
            // a SkinnedMesh or Mesh. Use the node's mesh reference
            // to mark SkinnedMesh if node has skin.
            if (nodeDef.skin !== undefined) {
  
              meshDefs[nodeDef.mesh].isSkinnedMesh = true;
  
            }
  
          }
  
        }
  
        this.json.meshReferences = meshReferences;
        this.json.meshUses = meshUses;
  
      };
  
      /**
       * Requests the specified dependency asynchronously, with caching.
       * @param {string} type
       * @param {number} index
       * @return {Promise<THREE.Object3D|THREE.Material|THREE.Texture|THREE.AnimationClip|ArrayBuffer|Object>}
       */
      GLTFParser.prototype.getDependency = function (type, index) {
  
        var cacheKey = type + ':' + index;
        var dependency = this.cache.get(cacheKey);
  
        if (!dependency) {
  
          switch (type) {
  
            case 'scene':
              dependency = this.loadScene(index);
              break;
  
            case 'node':
              dependency = this.loadNode(index);
              break;
  
            case 'mesh':
              dependency = this.loadMesh(index);
              break;
  
            case 'accessor':
              dependency = this.loadAccessor(index);
              break;
  
            case 'bufferView':
              dependency = this.loadBufferView(index);
              break;
  
            case 'buffer':
              dependency = this.loadBuffer(index);
              break;
  
            case 'material':
              dependency = this.loadMaterial(index);
              break;
  
            case 'texture':
              dependency = this.loadTexture(index);
              break;
  
            case 'skin':
              dependency = this.loadSkin(index);
              break;
  
            case 'animation':
              dependency = this.loadAnimation(index);
              break;
  
            case 'camera':
              dependency = this.loadCamera(index);
              break;
  
            case 'light':
              dependency = this.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL].loadLight(index);
              break;
  
            default:
              throw new Error('Unknown type: ' + type);
  
          }
  
          this.cache.add(cacheKey, dependency);
  
        }
  
        return dependency;
  
      };
  
      /**
       * Requests all dependencies of the specified type asynchronously, with caching.
       * @param {string} type
       * @return {Promise<Array<Object>>}
       */
      GLTFParser.prototype.getDependencies = function (type) {
  
        var dependencies = this.cache.get(type);
  
        if (!dependencies) {
  
          var parser = this;
          var defs = this.json[type + (type === 'mesh' ? 'es' : 's')] || [];
  
          dependencies = Promise.all(defs.map(function (def, index) {
  
            return parser.getDependency(type, index);
  
          }));
  
          this.cache.add(type, dependencies);
  
        }
  
        return dependencies;
  
      };
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
       * @param {number} bufferIndex
       * @return {Promise<ArrayBuffer>}
       */
      GLTFParser.prototype.loadBuffer = function (bufferIndex) {
  
        var bufferDef = this.json.buffers[bufferIndex];
        var loader = this.fileLoader;
  
        if (bufferDef.type && bufferDef.type !== 'arraybuffer') {
  
          throw new Error('THREE.GLTFLoader: ' + bufferDef.type + ' buffer type is not supported.');
  
        }
  
        // If present, GLB container is required to be the first buffer.
        if (bufferDef.uri === undefined && bufferIndex === 0) {
  
          return Promise.resolve(this.extensions[EXTENSIONS.KHR_BINARY_GLTF].body);
  
        }
  
        var options = this.options;
  
        return new Promise(function (resolve, reject) {
  
          loader.load(resolveURL(bufferDef.uri, options.path), resolve, undefined, function () {
  
            reject(new Error('THREE.GLTFLoader: Failed to load buffer "' + bufferDef.uri + '".'));
  
          });
  
        });
  
      };
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
       * @param {number} bufferViewIndex
       * @return {Promise<ArrayBuffer>}
       */
      GLTFParser.prototype.loadBufferView = function (bufferViewIndex) {
  
        var bufferViewDef = this.json.bufferViews[bufferViewIndex];
  
        return this.getDependency('buffer', bufferViewDef.buffer).then(function (buffer) {
  
          var byteLength = bufferViewDef.byteLength || 0;
          var byteOffset = bufferViewDef.byteOffset || 0;
          return buffer.slice(byteOffset, byteOffset + byteLength);
  
        });
  
      };
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#accessors
       * @param {number} accessorIndex
       * @return {Promise<THREE.BufferAttribute|THREE.InterleavedBufferAttribute>}
       */
      GLTFParser.prototype.loadAccessor = function (accessorIndex) {
  
        var parser = this;
        var json = this.json;
  
        var accessorDef = this.json.accessors[accessorIndex];
  
        if (accessorDef.bufferView === undefined && accessorDef.sparse === undefined) {
  
          // Ignore empty accessors, which may be used to declare runtime
          // information about attributes coming from another source (e.g. Draco
          // compression extension).
          return Promise.resolve(null);
  
        }
  
        var pendingBufferViews = [];
  
        if (accessorDef.bufferView !== undefined) {
  
          pendingBufferViews.push(this.getDependency('bufferView', accessorDef.bufferView));
  
        } else {
  
          pendingBufferViews.push(null);
  
        }
  
        if (accessorDef.sparse !== undefined) {
  
          pendingBufferViews.push(this.getDependency('bufferView', accessorDef.sparse.indices.bufferView));
          pendingBufferViews.push(this.getDependency('bufferView', accessorDef.sparse.values.bufferView));
  
        }
  
        return Promise.all(pendingBufferViews).then(function (bufferViews) {
  
          var bufferView = bufferViews[0];
  
          var itemSize = WEBGL_TYPE_SIZES[accessorDef.type];
          var TypedArray = WEBGL_COMPONENT_TYPES[accessorDef.componentType];
  
          // For VEC3: itemSize is 3, elementBytes is 4, itemBytes is 12.
          var elementBytes = TypedArray.BYTES_PER_ELEMENT;
          var itemBytes = elementBytes * itemSize;
          var byteOffset = accessorDef.byteOffset || 0;
          var byteStride = accessorDef.bufferView !== undefined ? json.bufferViews[accessorDef.bufferView].byteStride : undefined;
          var normalized = accessorDef.normalized === true;
          var array, bufferAttribute;
  
          // The buffer is not interleaved if the stride is the item size in bytes.
          if (byteStride && byteStride !== itemBytes) {
  
            // Each "slice" of the buffer, as defined by 'count' elements of 'byteStride' bytes, gets its own InterleavedBuffer
            // This makes sure that IBA.count reflects accessor.count properly
            var ibSlice = Math.floor(byteOffset / byteStride);
            var ibCacheKey = 'InterleavedBuffer:' + accessorDef.bufferView + ':' + accessorDef.componentType + ':' + ibSlice + ':' + accessorDef.count;
            var ib = parser.cache.get(ibCacheKey);
  
            if (!ib) {
  
              array = new TypedArray(bufferView, ibSlice * byteStride, accessorDef.count * byteStride / elementBytes);
  
              // Integer parameters to IB/IBA are in array elements, not bytes.
              ib = new THREE.InterleavedBuffer(array, byteStride / elementBytes);
  
              parser.cache.add(ibCacheKey, ib);
  
            }
  
            bufferAttribute = new THREE.InterleavedBufferAttribute(ib, itemSize, (byteOffset % byteStride) / elementBytes, normalized);
  
          } else {
  
            if (bufferView === null) {
  
              array = new TypedArray(accessorDef.count * itemSize);
  
            } else {
  
              array = new TypedArray(bufferView, byteOffset, accessorDef.count * itemSize);
  
            }
  
            bufferAttribute = new THREE.BufferAttribute(array, itemSize, normalized);
  
          }
  
          // https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#sparse-accessors
          if (accessorDef.sparse !== undefined) {
  
            var itemSizeIndices = WEBGL_TYPE_SIZES.SCALAR;
            var TypedArrayIndices = WEBGL_COMPONENT_TYPES[accessorDef.sparse.indices.componentType];
  
            var byteOffsetIndices = accessorDef.sparse.indices.byteOffset || 0;
            var byteOffsetValues = accessorDef.sparse.values.byteOffset || 0;
  
            var sparseIndices = new TypedArrayIndices(bufferViews[1], byteOffsetIndices, accessorDef.sparse.count * itemSizeIndices);
            var sparseValues = new TypedArray(bufferViews[2], byteOffsetValues, accessorDef.sparse.count * itemSize);
  
            if (bufferView !== null) {
  
              // Avoid modifying the original ArrayBuffer, if the bufferView wasn't initialized with zeroes.
              bufferAttribute.setArray(bufferAttribute.array.slice());
  
            }
  
            for (var i = 0, il = sparseIndices.length; i < il; i++) {
  
              var index = sparseIndices[i];
  
              bufferAttribute.setX(index, sparseValues[i * itemSize]);
              if (itemSize >= 2) bufferAttribute.setY(index, sparseValues[i * itemSize + 1]);
              if (itemSize >= 3) bufferAttribute.setZ(index, sparseValues[i * itemSize + 2]);
              if (itemSize >= 4) bufferAttribute.setW(index, sparseValues[i * itemSize + 3]);
              if (itemSize >= 5) throw new Error('THREE.GLTFLoader: Unsupported itemSize in sparse BufferAttribute.');
  
            }
  
          }
  
          return bufferAttribute;
  
        });
  
      };
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#textures
       * @param {number} textureIndex
       * @return {Promise<THREE.Texture>}
       */
      GLTFParser.prototype.loadTexture = function (textureIndex) {
  
        var parser = this;
        var json = this.json;
        var options = this.options;
        var textureLoader = this.textureLoader;
  
        // modified
        // var URL = window.URL || window.webkitURL;
        var URL = {};
        var textureDef = json.textures[textureIndex];
        var textureExtensions = textureDef.extensions || {};

        var source;
  
        if (textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS]) {
  
          source = json.images[textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS].source];
  
        } else {
  
          source = json.images[textureDef.source];
  
        }
  
        var sourceURI = source.uri;
        var isObjectURL = false;
  
        if (source.bufferView !== undefined) {
  
          // Load binary image data from bufferView, if provided.
  
          sourceURI = parser.getDependency('bufferView', source.bufferView).then(function (bufferView) {
  
            isObjectURL = true;
            var blob = new Blob([bufferView], { type: source.mimeType });
            sourceURI = URL.createObjectURL(blob);
            return sourceURI;
  
          });
  
        }
  
        return Promise.resolve(sourceURI).then(function (sourceURI) {
  
          // Load Texture resource.
  
          var loader = THREE.Loader.Handlers.get(sourceURI);
  
          if (!loader) {
  
            loader = textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS]
              ? parser.extensions[EXTENSIONS.MSFT_TEXTURE_DDS].ddsLoader
              : textureLoader;
  
          }
  
          return new Promise(function (resolve, reject) {
  
            loader.load(resolveURL(sourceURI, options.path), resolve, undefined, reject);
  
          });
  
        }).then(function (texture) {
  
          // Clean up resources and configure Texture.
  
          if (isObjectURL === true) {
  
            URL.revokeObjectURL(sourceURI);
  
          }
  
          texture.flipY = false;
  
          if (textureDef.name !== undefined) texture.name = textureDef.name;
  
          // Ignore unknown mime types, like DDS files.
          if (source.mimeType in MIME_TYPE_FORMATS) {
  
            texture.format = MIME_TYPE_FORMATS[source.mimeType];
  
          }
  
          var samplers = json.samplers || {};
          var sampler = samplers[textureDef.sampler] || {};
  
          texture.magFilter = WEBGL_FILTERS[sampler.magFilter] || THREE.LinearFilter;
          texture.minFilter = WEBGL_FILTERS[sampler.minFilter] || THREE.LinearMipmapLinearFilter;
          texture.wrapS = WEBGL_WRAPPINGS[sampler.wrapS] || THREE.RepeatWrapping;
          texture.wrapT = WEBGL_WRAPPINGS[sampler.wrapT] || THREE.RepeatWrapping;
  
          return texture;
  
        });
  
      };
  
      /**
       * Asynchronously assigns a texture to the given material parameters.
       * @param {Object} materialParams
       * @param {string} mapName
       * @param {Object} mapDef
       * @return {Promise}
       */
      GLTFParser.prototype.assignTexture = function (materialParams, mapName, mapDef) {
  
        var parser = this;
  
        return this.getDependency('texture', mapDef.index).then(function (texture) {
  
          if (!texture.isCompressedTexture) {
  
            switch (mapName) {
  
              case 'aoMap':
              case 'emissiveMap':
              case 'metalnessMap':
              case 'normalMap':
              case 'roughnessMap':
                texture.format = THREE.RGBFormat;
                break;
  
            }
  
          }
  
          if (parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM]) {
  
            var transform = mapDef.extensions !== undefined ? mapDef.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM] : undefined;
  
            if (transform) {
  
              texture = parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM].extendTexture(texture, transform);
  
            }
  
          }
  
          materialParams[mapName] = texture;
  
        });
  
      };
  
      /**
       * Assigns final material to a Mesh, Line, or Points instance. The instance
       * already has a material (generated from the glTF material options alone)
       * but reuse of the same glTF material may require multiple threejs materials
       * to accomodate different primitive types, defines, etc. New materials will
       * be created if necessary, and reused from a cache.
       * @param  {THREE.Object3D} mesh Mesh, Line, or Points instance.
       */
      GLTFParser.prototype.assignFinalMaterial = function (mesh) {
  
        var geometry = mesh.geometry;
        var material = mesh.material;
        var extensions = this.extensions;
  
        var useVertexTangents = geometry.attributes.tangent !== undefined;
        var useVertexColors = geometry.attributes.color !== undefined;
        var useFlatShading = geometry.attributes.normal === undefined;
        var useSkinning = mesh.isSkinnedMesh === true;
        var useMorphTargets = Object.keys(geometry.morphAttributes).length > 0;
        var useMorphNormals = useMorphTargets && geometry.morphAttributes.normal !== undefined;
  
        if (mesh.isPoints) {
  
          var cacheKey = 'PointsMaterial:' + material.uuid;
  
          var pointsMaterial = this.cache.get(cacheKey);
  
          if (!pointsMaterial) {
  
            pointsMaterial = new THREE.PointsMaterial();
            THREE.Material.prototype.copy.call(pointsMaterial, material);
            pointsMaterial.color.copy(material.color);
            pointsMaterial.map = material.map;
            pointsMaterial.lights = false; // PointsMaterial doesn't support lights yet
            pointsMaterial.sizeAttenuation = false; // glTF spec says points should be 1px
  
            this.cache.add(cacheKey, pointsMaterial);
  
          }
  
          material = pointsMaterial;
  
        } else if (mesh.isLine) {
  
          var cacheKey = 'LineBasicMaterial:' + material.uuid;
  
          var lineMaterial = this.cache.get(cacheKey);
  
          if (!lineMaterial) {
  
            lineMaterial = new THREE.LineBasicMaterial();
            THREE.Material.prototype.copy.call(lineMaterial, material);
            lineMaterial.color.copy(material.color);
            lineMaterial.lights = false; // LineBasicMaterial doesn't support lights yet
  
            this.cache.add(cacheKey, lineMaterial);
  
          }
  
          material = lineMaterial;
  
        }
  
        // Clone the material if it will be modified
        if (useVertexTangents || useVertexColors || useFlatShading || useSkinning || useMorphTargets) {
  
          var cacheKey = 'ClonedMaterial:' + material.uuid + ':';
  
          if (material.isGLTFSpecularGlossinessMaterial) cacheKey += 'specular-glossiness:';
          if (useSkinning) cacheKey += 'skinning:';
          if (useVertexTangents) cacheKey += 'vertex-tangents:';
          if (useVertexColors) cacheKey += 'vertex-colors:';
          if (useFlatShading) cacheKey += 'flat-shading:';
          if (useMorphTargets) cacheKey += 'morph-targets:';
          if (useMorphNormals) cacheKey += 'morph-normals:';
  
          var cachedMaterial = this.cache.get(cacheKey);
  
          if (!cachedMaterial) {
  
            cachedMaterial = material.isGLTFSpecularGlossinessMaterial
              ? extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].cloneMaterial(material)
              : material.clone();
  
            if (useSkinning) cachedMaterial.skinning = true;
            if (useVertexTangents) cachedMaterial.vertexTangents = true;
            if (useVertexColors) cachedMaterial.vertexColors = THREE.VertexColors;
            if (useFlatShading) cachedMaterial.flatShading = true;
            if (useMorphTargets) cachedMaterial.morphTargets = true;
            if (useMorphNormals) cachedMaterial.morphNormals = true;
  
            this.cache.add(cacheKey, cachedMaterial);
  
          }
  
          material = cachedMaterial;
  
        }
  
        // workarounds for mesh and geometry
  
        if (material.aoMap && geometry.attributes.uv2 === undefined && geometry.attributes.uv !== undefined) {
  
          console.log('THREE.GLTFLoader: Duplicating UVs to support aoMap.');
          geometry.addAttribute('uv2', new THREE.BufferAttribute(geometry.attributes.uv.array, 2));
  
        }
  
        if (material.isGLTFSpecularGlossinessMaterial) {
  
          // for GLTFSpecularGlossinessMaterial(ShaderMaterial) uniforms runtime update
          mesh.onBeforeRender = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].refreshUniforms;
  
        }
  
        mesh.material = material;
  
      };
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#materials
       * @param {number} materialIndex
       * @return {Promise<THREE.Material>}
       */
      GLTFParser.prototype.loadMaterial = function (materialIndex) {
  
        var parser = this;
        var json = this.json;
        var extensions = this.extensions;
        var materialDef = json.materials[materialIndex];
  
        var materialType;
        var materialParams = {};
        var materialExtensions = materialDef.extensions || {};
  
        var pending = [];
  
        if (materialExtensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS]) {
  
          var sgExtension = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS];
          materialType = sgExtension.getMaterialType();
          pending.push(sgExtension.extendParams(materialParams, materialDef, parser));
  
        } else if (materialExtensions[EXTENSIONS.KHR_MATERIALS_UNLIT]) {
  
          var kmuExtension = extensions[EXTENSIONS.KHR_MATERIALS_UNLIT];
          materialType = kmuExtension.getMaterialType();
          pending.push(kmuExtension.extendParams(materialParams, materialDef, parser));
  
        } else {
  
          // Specification:
          // https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#metallic-roughness-material
  
          materialType = THREE.MeshStandardMaterial;
  
          var metallicRoughness = materialDef.pbrMetallicRoughness || {};
  
          materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
          materialParams.opacity = 1.0;
  
          if (Array.isArray(metallicRoughness.baseColorFactor)) {
  
            var array = metallicRoughness.baseColorFactor;
  
            materialParams.color.fromArray(array);
            materialParams.opacity = array[3];
  
          }
  
          if (metallicRoughness.baseColorTexture !== undefined) {
  
            pending.push(parser.assignTexture(materialParams, 'map', metallicRoughness.baseColorTexture));
  
          }
  
          materialParams.metalness = metallicRoughness.metallicFactor !== undefined ? metallicRoughness.metallicFactor : 1.0;
          materialParams.roughness = metallicRoughness.roughnessFactor !== undefined ? metallicRoughness.roughnessFactor : 1.0;
  
          if (metallicRoughness.metallicRoughnessTexture !== undefined) {
  
            pending.push(parser.assignTexture(materialParams, 'metalnessMap', metallicRoughness.metallicRoughnessTexture));
            pending.push(parser.assignTexture(materialParams, 'roughnessMap', metallicRoughness.metallicRoughnessTexture));
  
          }
  
        }
  
        if (materialDef.doubleSided === true) {
  
          materialParams.side = THREE.DoubleSide;
  
        }
  
        var alphaMode = materialDef.alphaMode || ALPHA_MODES.OPAQUE;
  
        if (alphaMode === ALPHA_MODES.BLEND) {
  
          materialParams.transparent = true;
  
        } else {
  
          materialParams.transparent = false;
  
          if (alphaMode === ALPHA_MODES.MASK) {
  
            materialParams.alphaTest = materialDef.alphaCutoff !== undefined ? materialDef.alphaCutoff : 0.5;
  
          }
  
        }
  
        if (materialDef.normalTexture !== undefined && materialType !== THREE.MeshBasicMaterial) {
  
          pending.push(parser.assignTexture(materialParams, 'normalMap', materialDef.normalTexture));
  
          materialParams.normalScale = new THREE.Vector2(1, 1);
  
          if (materialDef.normalTexture.scale !== undefined) {
  
            materialParams.normalScale.set(materialDef.normalTexture.scale, materialDef.normalTexture.scale);
  
          }
  
        }
  
        if (materialDef.occlusionTexture !== undefined && materialType !== THREE.MeshBasicMaterial) {
  
          pending.push(parser.assignTexture(materialParams, 'aoMap', materialDef.occlusionTexture));
  
          if (materialDef.occlusionTexture.strength !== undefined) {
  
            materialParams.aoMapIntensity = materialDef.occlusionTexture.strength;
  
          }
  
        }
  
        if (materialDef.emissiveFactor !== undefined && materialType !== THREE.MeshBasicMaterial) {
  
          materialParams.emissive = new THREE.Color().fromArray(materialDef.emissiveFactor);
  
        }
  
        if (materialDef.emissiveTexture !== undefined && materialType !== THREE.MeshBasicMaterial) {
  
          pending.push(parser.assignTexture(materialParams, 'emissiveMap', materialDef.emissiveTexture));
  
        }
  
        return Promise.all(pending).then(function () {
  
          var material;
  
          if (materialType === THREE.ShaderMaterial) {
  
            material = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].createMaterial(materialParams);
  
          } else {
  
            material = new materialType(materialParams);
  
          }
  
          if (materialDef.name !== undefined) material.name = materialDef.name;
  
          // baseColorTexture, emissiveTexture, and specularGlossinessTexture use sRGB encoding.
          if (material.map) material.map.encoding = THREE.sRGBEncoding;
          if (material.emissiveMap) material.emissiveMap.encoding = THREE.sRGBEncoding;
          if (material.specularMap) material.specularMap.encoding = THREE.sRGBEncoding;
  
          assignExtrasToUserData(material, materialDef);
  
          if (materialDef.extensions) addUnknownExtensionsToUserData(extensions, material, materialDef);
  
          return material;
  
        });
  
      };
  
      /**
       * @param {THREE.BufferGeometry} geometry
       * @param {GLTF.Primitive} primitiveDef
       * @param {GLTFParser} parser
       * @return {Promise<THREE.BufferGeometry>}
       */
      function addPrimitiveAttributes(geometry, primitiveDef, parser) {
  
        var attributes = primitiveDef.attributes;
  
        var pending = [];
  
        function assignAttributeAccessor(accessorIndex, attributeName) {
  
          return parser.getDependency('accessor', accessorIndex)
            .then(function (accessor) {
  
              geometry.addAttribute(attributeName, accessor);
  
            });
  
        }
  
        for (var gltfAttributeName in attributes) {
  
          var threeAttributeName = ATTRIBUTES[gltfAttributeName] || gltfAttributeName.toLowerCase();
  
          // Skip attributes already provided by e.g. Draco extension.
          if (threeAttributeName in geometry.attributes) continue;
  
          pending.push(assignAttributeAccessor(attributes[gltfAttributeName], threeAttributeName));
  
        }
  
        if (primitiveDef.indices !== undefined && !geometry.index) {
  
          var accessor = parser.getDependency('accessor', primitiveDef.indices).then(function (accessor) {
  
            geometry.setIndex(accessor);
  
          });
  
          pending.push(accessor);
  
        }
  
        assignExtrasToUserData(geometry, primitiveDef);
  
        return Promise.all(pending).then(function () {
  
          return primitiveDef.targets !== undefined
            ? addMorphTargets(geometry, primitiveDef.targets, parser)
            : geometry;
  
        });
  
      }
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#geometry
       *
       * Creates BufferGeometries from primitives.
       *
       * @param {Array<GLTF.Primitive>} primitives
       * @return {Promise<Array<THREE.BufferGeometry>>}
       */
      GLTFParser.prototype.loadGeometries = function (primitives) {
  
        var parser = this;
        var extensions = this.extensions;
        var cache = this.primitiveCache;
  
        function createDracoPrimitive(primitive) {
  
          return extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]
            .decodePrimitive(primitive, parser)
            .then(function (geometry) {
  
              return addPrimitiveAttributes(geometry, primitive, parser);
  
            });
  
        }
  
        var pending = [];
  
        for (var i = 0, il = primitives.length; i < il; i++) {
  
          var primitive = primitives[i];
          var cacheKey = createPrimitiveKey(primitive);
  
          // See if we've already created this geometry
          var cached = cache[cacheKey];
  
          if (cached) {
  
            // Use the cached geometry if it exists
            pending.push(cached.promise);
  
          } else {
  
            var geometryPromise;
  
            if (primitive.extensions && primitive.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]) {
  
              // Use DRACO geometry if available
              geometryPromise = createDracoPrimitive(primitive);
  
            } else {
  
              // Otherwise create a new geometry
              geometryPromise = addPrimitiveAttributes(new THREE.BufferGeometry(), primitive, parser);
  
            }
  
            // Cache this geometry
            cache[cacheKey] = { primitive: primitive, promise: geometryPromise };
  
            pending.push(geometryPromise);
  
          }
  
        }
  
        return Promise.all(pending);
  
      };
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#meshes
       * @param {number} meshIndex
       * @return {Promise<THREE.Group|THREE.Mesh|THREE.SkinnedMesh>}
       */
      GLTFParser.prototype.loadMesh = function (meshIndex) {
  
        var parser = this;
        var json = this.json;
  
        var meshDef = json.meshes[meshIndex];
        var primitives = meshDef.primitives;
  
        var pending = [];
  
        for (var i = 0, il = primitives.length; i < il; i++) {
  
          var material = primitives[i].material === undefined
            ? createDefaultMaterial()
            : this.getDependency('material', primitives[i].material);
  
          pending.push(material);
  
        }
  
        return Promise.all(pending).then(function (originalMaterials) {
  
          return parser.loadGeometries(primitives).then(function (geometries) {
  
            var meshes = [];
  
            for (var i = 0, il = geometries.length; i < il; i++) {
  
              var geometry = geometries[i];
              var primitive = primitives[i];
  
              // 1. create Mesh
  
              var mesh;
  
              var material = originalMaterials[i];
  
              if (primitive.mode === WEBGL_CONSTANTS.TRIANGLES ||
                primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ||
                primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ||
                primitive.mode === undefined) {
  
                // .isSkinnedMesh isn't in glTF spec. See .markDefs()
                mesh = meshDef.isSkinnedMesh === true
                  ? new THREE.SkinnedMesh(geometry, material)
                  : new THREE.Mesh(geometry, material);
  
                if (mesh.isSkinnedMesh === true && !mesh.geometry.attributes.skinWeight.normalized) {
  
                  // we normalize floating point skin weight array to fix malformed assets (see #15319)
                  // it's important to skip this for non-float32 data since normalizeSkinWeights assumes non-normalized inputs
                  mesh.normalizeSkinWeights();
  
                }
  
                if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP) {
  
                  mesh.drawMode = THREE.TriangleStripDrawMode;
  
                } else if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN) {
  
                  mesh.drawMode = THREE.TriangleFanDrawMode;
  
                }
  
              } else if (primitive.mode === WEBGL_CONSTANTS.LINES) {
  
                mesh = new THREE.LineSegments(geometry, material);
  
              } else if (primitive.mode === WEBGL_CONSTANTS.LINE_STRIP) {
  
                mesh = new THREE.Line(geometry, material);
  
              } else if (primitive.mode === WEBGL_CONSTANTS.LINE_LOOP) {
  
                mesh = new THREE.LineLoop(geometry, material);
  
              } else if (primitive.mode === WEBGL_CONSTANTS.POINTS) {
  
                mesh = new THREE.Points(geometry, material);
  
              } else {
  
                throw new Error('THREE.GLTFLoader: Primitive mode unsupported: ' + primitive.mode);
  
              }
  
              if (Object.keys(mesh.geometry.morphAttributes).length > 0) {
  
                updateMorphTargets(mesh, meshDef);
  
              }
  
              mesh.name = meshDef.name || ('mesh_' + meshIndex);
  
              if (geometries.length > 1) mesh.name += '_' + i;
  
              assignExtrasToUserData(mesh, meshDef);
  
              parser.assignFinalMaterial(mesh);
  
              meshes.push(mesh);
  
            }
  
            if (meshes.length === 1) {
  
              return meshes[0];
  
            }
  
            var group = new THREE.Group();
  
            for (var i = 0, il = meshes.length; i < il; i++) {
  
              group.add(meshes[i]);
  
            }
  
            return group;
  
          });
  
        });
  
      };
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#cameras
       * @param {number} cameraIndex
       * @return {Promise<THREE.Camera>}
       */
      GLTFParser.prototype.loadCamera = function (cameraIndex) {
  
        var camera;
        var cameraDef = this.json.cameras[cameraIndex];
        var params = cameraDef[cameraDef.type];
  
        if (!params) {
  
          console.warn('THREE.GLTFLoader: Missing camera parameters.');
          return;
  
        }
  
        if (cameraDef.type === 'perspective') {
  
          camera = new THREE.PerspectiveCamera(THREE.Math.radToDeg(params.yfov), params.aspectRatio || 1, params.znear || 1, params.zfar || 2e6);
  
        } else if (cameraDef.type === 'orthographic') {
  
          camera = new THREE.OrthographicCamera(params.xmag / - 2, params.xmag / 2, params.ymag / 2, params.ymag / - 2, params.znear, params.zfar);
  
        }
  
        if (cameraDef.name !== undefined) camera.name = cameraDef.name;
  
        assignExtrasToUserData(camera, cameraDef);
  
        return Promise.resolve(camera);
  
      };
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#skins
       * @param {number} skinIndex
       * @return {Promise<Object>}
       */
      GLTFParser.prototype.loadSkin = function (skinIndex) {
  
        var skinDef = this.json.skins[skinIndex];
  
        var skinEntry = { joints: skinDef.joints };
  
        if (skinDef.inverseBindMatrices === undefined) {
  
          return Promise.resolve(skinEntry);
  
        }
  
        return this.getDependency('accessor', skinDef.inverseBindMatrices).then(function (accessor) {
  
          skinEntry.inverseBindMatrices = accessor;
  
          return skinEntry;
  
        });
  
      };
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#animations
       * @param {number} animationIndex
       * @return {Promise<THREE.AnimationClip>}
       */
      GLTFParser.prototype.loadAnimation = function (animationIndex) {
  
        var json = this.json;
  
        var animationDef = json.animations[animationIndex];
  
        var pendingNodes = [];
        var pendingInputAccessors = [];
        var pendingOutputAccessors = [];
        var pendingSamplers = [];
        var pendingTargets = [];
  
        for (var i = 0, il = animationDef.channels.length; i < il; i++) {
  
          var channel = animationDef.channels[i];
          var sampler = animationDef.samplers[channel.sampler];
          var target = channel.target;
          var name = target.node !== undefined ? target.node : target.id; // NOTE: target.id is deprecated.
          var input = animationDef.parameters !== undefined ? animationDef.parameters[sampler.input] : sampler.input;
          var output = animationDef.parameters !== undefined ? animationDef.parameters[sampler.output] : sampler.output;
  
          pendingNodes.push(this.getDependency('node', name));
          pendingInputAccessors.push(this.getDependency('accessor', input));
          pendingOutputAccessors.push(this.getDependency('accessor', output));
          pendingSamplers.push(sampler);
          pendingTargets.push(target);
  
        }
  
        return Promise.all([
  
          Promise.all(pendingNodes),
          Promise.all(pendingInputAccessors),
          Promise.all(pendingOutputAccessors),
          Promise.all(pendingSamplers),
          Promise.all(pendingTargets)
  
        ]).then(function (dependencies) {
  
          var nodes = dependencies[0];
          var inputAccessors = dependencies[1];
          var outputAccessors = dependencies[2];
          var samplers = dependencies[3];
          var targets = dependencies[4];
  
          var tracks = [];
  
          for (var i = 0, il = nodes.length; i < il; i++) {
  
            var node = nodes[i];
            var inputAccessor = inputAccessors[i];
            var outputAccessor = outputAccessors[i];
            var sampler = samplers[i];
            var target = targets[i];
  
            if (node === undefined) continue;
  
            node.updateMatrix();
            node.matrixAutoUpdate = true;
  
            var TypedKeyframeTrack;
  
            switch (PATH_PROPERTIES[target.path]) {
  
              case PATH_PROPERTIES.weights:
  
                TypedKeyframeTrack = THREE.NumberKeyframeTrack;
                break;
  
              case PATH_PROPERTIES.rotation:
  
                TypedKeyframeTrack = THREE.QuaternionKeyframeTrack;
                break;
  
              case PATH_PROPERTIES.position:
              case PATH_PROPERTIES.scale:
              default:
  
                TypedKeyframeTrack = THREE.VectorKeyframeTrack;
                break;
  
            }
  
            var targetName = node.name ? node.name : node.uuid;
  
            var interpolation = sampler.interpolation !== undefined ? INTERPOLATION[sampler.interpolation] : THREE.InterpolateLinear;
  
            var targetNames = [];
  
            if (PATH_PROPERTIES[target.path] === PATH_PROPERTIES.weights) {
  
              // Node may be a THREE.Group (glTF mesh with several primitives) or a THREE.Mesh.
              node.traverse(function (object) {
  
                if (object.isMesh === true && object.morphTargetInfluences) {
  
                  targetNames.push(object.name ? object.name : object.uuid);
  
                }
  
              });
  
            } else {
  
              targetNames.push(targetName);
  
            }
  
            var outputArray = outputAccessor.array;
  
            if (outputAccessor.normalized) {
  
              var scale;
  
              if (outputArray.constructor === Int8Array) {
  
                scale = 1 / 127;
  
              } else if (outputArray.constructor === Uint8Array) {
  
                scale = 1 / 255;
  
              } else if (outputArray.constructor == Int16Array) {
  
                scale = 1 / 32767;
  
              } else if (outputArray.constructor === Uint16Array) {
  
                scale = 1 / 65535;
  
              } else {
  
                throw new Error('THREE.GLTFLoader: Unsupported output accessor component type.');
  
              }
  
              var scaled = new Float32Array(outputArray.length);
  
              for (var j = 0, jl = outputArray.length; j < jl; j++) {
  
                scaled[j] = outputArray[j] * scale;
  
              }
  
              outputArray = scaled;
  
            }
  
            for (var j = 0, jl = targetNames.length; j < jl; j++) {
  
              var track = new TypedKeyframeTrack(
                targetNames[j] + '.' + PATH_PROPERTIES[target.path],
                inputAccessor.array,
                outputArray,
                interpolation
              );
  
              // Override interpolation with custom factory method.
              if (sampler.interpolation === 'CUBICSPLINE') {
  
                track.createInterpolant = function InterpolantFactoryMethodGLTFCubicSpline(result) {
  
                  // A CUBICSPLINE keyframe in glTF has three output values for each input value,
                  // representing inTangent, splineVertex, and outTangent. As a result, track.getValueSize()
                  // must be divided by three to get the interpolant's sampleSize argument.
  
                  return new GLTFCubicSplineInterpolant(this.times, this.values, this.getValueSize() / 3, result);
  
                };
  
                // Mark as CUBICSPLINE. `track.getInterpolation()` doesn't support custom interpolants.
                track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline = true;
  
              }
  
              tracks.push(track);
  
            }
  
          }
  
          var name = animationDef.name !== undefined ? animationDef.name : 'animation_' + animationIndex;
  
          return new THREE.AnimationClip(name, undefined, tracks);
  
        });
  
      };
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#nodes-and-hierarchy
       * @param {number} nodeIndex
       * @return {Promise<THREE.Object3D>}
       */
      GLTFParser.prototype.loadNode = function (nodeIndex) {
  
        var json = this.json;
        var extensions = this.extensions;
        var parser = this;
  
        var meshReferences = json.meshReferences;
        var meshUses = json.meshUses;
  
        var nodeDef = json.nodes[nodeIndex];
  
        return (function () {
  
          var pending = [];
  
          if (nodeDef.mesh !== undefined) {
  
            pending.push(parser.getDependency('mesh', nodeDef.mesh).then(function (mesh) {
  
              var node;
  
              if (meshReferences[nodeDef.mesh] > 1) {
  
                var instanceNum = meshUses[nodeDef.mesh]++;
  
                node = mesh.clone();
                node.name += '_instance_' + instanceNum;
  
                // onBeforeRender copy for Specular-Glossiness
                node.onBeforeRender = mesh.onBeforeRender;
  
                for (var i = 0, il = node.children.length; i < il; i++) {
  
                  node.children[i].name += '_instance_' + instanceNum;
                  node.children[i].onBeforeRender = mesh.children[i].onBeforeRender;
  
                }
  
              } else {
  
                node = mesh;
  
              }
  
              // if weights are provided on the node, override weights on the mesh.
              if (nodeDef.weights !== undefined) {
  
                node.traverse(function (o) {
  
                  if (!o.isMesh) return;
  
                  for (var i = 0, il = nodeDef.weights.length; i < il; i++) {
  
                    o.morphTargetInfluences[i] = nodeDef.weights[i];
  
                  }
  
                });
  
              }
  
              return node;
  
            }));
  
          }
  
          if (nodeDef.camera !== undefined) {
  
            pending.push(parser.getDependency('camera', nodeDef.camera));
  
          }
  
          if (nodeDef.extensions
            && nodeDef.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL]
            && nodeDef.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL].light !== undefined) {
  
            pending.push(parser.getDependency('light', nodeDef.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL].light));
  
          }
  
          return Promise.all(pending);
  
        }()).then(function (objects) {
  
          var node;
  
          // .isBone isn't in glTF spec. See .markDefs
          if (nodeDef.isBone === true) {
  
            node = new THREE.Bone();
  
          } else if (objects.length > 1) {
  
            node = new THREE.Group();
  
          } else if (objects.length === 1) {
  
            node = objects[0];
  
          } else {
  
            node = new THREE.Object3D();
  
          }
  
          if (node !== objects[0]) {
  
            for (var i = 0, il = objects.length; i < il; i++) {
  
              node.add(objects[i]);
  
            }
  
          }
  
          if (nodeDef.name !== undefined) {
  
            node.userData.name = nodeDef.name;
            node.name = THREE.PropertyBinding.sanitizeNodeName(nodeDef.name);
  
          }
  
          assignExtrasToUserData(node, nodeDef);
  
          if (nodeDef.extensions) addUnknownExtensionsToUserData(extensions, node, nodeDef);
  
          if (nodeDef.matrix !== undefined) {
  
            var matrix = new THREE.Matrix4();
            matrix.fromArray(nodeDef.matrix);
            node.applyMatrix(matrix);
  
          } else {
  
            if (nodeDef.translation !== undefined) {
  
              node.position.fromArray(nodeDef.translation);
  
            }
  
            if (nodeDef.rotation !== undefined) {
  
              node.quaternion.fromArray(nodeDef.rotation);
  
            }
  
            if (nodeDef.scale !== undefined) {
  
              node.scale.fromArray(nodeDef.scale);
  
            }
  
          }
  
          return node;
  
        });
  
      };
  
      /**
       * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#scenes
       * @param {number} sceneIndex
       * @return {Promise<THREE.Scene>}
       */
      GLTFParser.prototype.loadScene = function () {
  
        // scene node hierachy builder
  
        function buildNodeHierachy(nodeId, parentObject, json, parser) {
  
          var nodeDef = json.nodes[nodeId];
  
          return parser.getDependency('node', nodeId).then(function (node) {
  
            if (nodeDef.skin === undefined) return node;
  
            // build skeleton here as well
  
            var skinEntry;
  
            return parser.getDependency('skin', nodeDef.skin).then(function (skin) {
  
              skinEntry = skin;
  
              var pendingJoints = [];
  
              for (var i = 0, il = skinEntry.joints.length; i < il; i++) {
  
                pendingJoints.push(parser.getDependency('node', skinEntry.joints[i]));
  
              }
  
              return Promise.all(pendingJoints);
  
            }).then(function (jointNodes) {
  
              node.traverse(function (mesh) {
  
                if (!mesh.isMesh) return;
  
                var bones = [];
                var boneInverses = [];
  
                for (var j = 0, jl = jointNodes.length; j < jl; j++) {
  
                  var jointNode = jointNodes[j];
  
                  if (jointNode) {
  
                    bones.push(jointNode);
  
                    var mat = new THREE.Matrix4();
  
                    if (skinEntry.inverseBindMatrices !== undefined) {
  
                      mat.fromArray(skinEntry.inverseBindMatrices.array, j * 16);
  
                    }
  
                    boneInverses.push(mat);
  
                  } else {
  
                    console.warn('THREE.GLTFLoader: Joint "%s" could not be found.', skinEntry.joints[j]);
  
                  }
  
                }
  
                mesh.bind(new THREE.Skeleton(bones, boneInverses), mesh.matrixWorld);
  
              });
  
              return node;
  
            });
  
          }).then(function (node) {
  
            // build node hierachy
  
            parentObject.add(node);
  
            var pending = [];
  
            if (nodeDef.children) {
  
              var children = nodeDef.children;
  
              for (var i = 0, il = children.length; i < il; i++) {
  
                var child = children[i];
                pending.push(buildNodeHierachy(child, node, json, parser));
  
              }
  
            }
  
            return Promise.all(pending);
  
          });
  
        }
  
        return function loadScene(sceneIndex) {
  
          var json = this.json;
          var extensions = this.extensions;
          var sceneDef = this.json.scenes[sceneIndex];
          var parser = this;
  
          var scene = new THREE.Scene();
          if (sceneDef.name !== undefined) scene.name = sceneDef.name;
  
          assignExtrasToUserData(scene, sceneDef);
  
          if (sceneDef.extensions) addUnknownExtensionsToUserData(extensions, scene, sceneDef);
  
          var nodeIds = sceneDef.nodes || [];
  
          var pending = [];
  
          for (var i = 0, il = nodeIds.length; i < il; i++) {
  
            pending.push(buildNodeHierachy(nodeIds[i], scene, json, parser));
  
          }
  
          return Promise.all(pending).then(function () {
  
            return scene;
  
          });
  
        };
  
      }();
  
      return GLTFLoader;
  
    })();
  }